1. Field of the Invention
The present invention relates to a raisable extruder head for extruders for shaping plastic mixtures of rubber or synthetic material; the extruder head includes parts which are pivotable about fixed points on the extruder head between a closed position and an open position, and which can be pressed against the extruder head, in the closed position, ahead of an interchangeable extruder nozzle.
2. Description of the Prior Art
Extruders having such extruder heads are used, for example, for manufacturing the uncured tread strips of pneumatic vehicle tires, or for other profiled articles having a flat, elongated cross-sectional shape, with such articles having either a homogeneous composition, or a multi-component construction. Free accessibility to the flow channels which lead to the extruder nozzle is usually required, so that each time that the mixture which is being processed is changed, these flow channels can be exposed and all residue can be thoroughly cleaned therefrom. By embodying the extruder heads in such a way that they can be opened, this requirement ia satisfied. For a sealing engagement of the extruder head parts, which form the wall of the flow channels and are movable relative to one another, heretofore known proposals provided for mechanical clamps or even hydraulically operated wedge-type slides which run up on inclined surfaces. In either case, due to the interaction of the interior material pressure, and due to the exterior closing forces, high bending moments are applied to the clamped or closed extruder head parts, and since even only slight gaps of an order of magnitude of a few hundredths of a millimeter between the sealing surfaces allow extrusion material to issue from the flow channels, the pertaining parts have to be made as rigid as possible. However, this leads to disproportionately heavy constructions of the extruder heads, accompanied by the drawbacks of heavy weight and high manufacturing costs, as well as impediments, caused by the geometry of the dimensioning, to the accessibility of the flow channels, thus making it more difficult to clean the latter.
An object of the present invention is to obtain a desired free accessibility to the channels which convey the extrusion material via a novel design of the extruder head, which can be opened, on extruders with a relatively light and simple construction.